I think it is Susan Rice now. I don't believe she really resigned. I think she got promoted in the Cabal and now runs things for the White House whereas before she resigned she was on a team of people. My guess is she had to be pulled out so she had time to actually do the day-to-day stuff the job requires, so she couldn't do her day job at the same time. She will be the behind-the-scenes person giving the orders to her old team.

Side thought - if Trump was still in the White House instead of Biden I think her move would be to actually run for (and steal) the Presidency. The optics of her running against Biden would be awful.